Information storage devices are used to retrieve and/or store data in computers and other consumer electronics devices. A magnetic hard disk drive is an example of an information storage device that includes one or more heads that can both read and write from one or more rotating storage media. In a magnetic hard disk drive device, each head is a sub-component of a head-gimbal assembly (HGA) that typically includes a laminated flexure to carry electrical signals to and from the head. The HGA, in turn, is a sub-component of a head-stack assembly (HSA) that typically includes one or more HGAs, an actuator, and a flexible printed circuit (FPC). The one or more HGAs are attached to various arms of the actuator.
Each of the laminated flexures typically includes electrically conductive traces (e.g., copper traces) that are isolated from a stainless steel structural layer by a dielectric layer such as a polyimide layer, and the conductive traces transfer signals between the head and the FPC on the actuator body. Each HGA flexure includes a flexure tail that is attached to the FPC adjacent the actuator body. That is, the conductive traces extend from adjacent the head and continue along the flexure to electrical connection points (or pads) located at the tail portion of the flexure. The FPC includes conductive electrical terminals (or bond pads) that correspond to the electrical connection points of the flexure tail.
To facilitate electrical connection of the conductive traces of the flexure tails to the conductive electrical terminals of the FPC during an HSA manufacturing process, the flexure tails are first properly positioned relative to the FPC so that the connection points of the flexure tails are aligned with the conductive electrical terminals of the FPC. Then, the flexure tails are held or constrained against the conductive electrical terminals of the FPC while the electrical connections are made (e.g., by ultrasonic bonding, solder jet bonding, solder bump reflow, or anisotropic conductive film bonding).
An anisotropic conductive film (ACF) is an adhesive doped with conductive beads or cylindrical particles of uniform or similar diameter. As the doped adhesive is compressed and cured, it is squeezed between the surfaces to be bonded with sufficient uniform pressure that a single layer of the conductive beads makes contact with both surfaces to be bonded. In this way, the thickness of the adhesive layer between the bonded surfaces becomes approximately equal to the size of the conductive beads. The cured adhesive film may conduct electricity via the contacting beads in a direction normal to the bonded surfaces (though may not necessarily conduct electricity parallel to the bonded surfaces, since the beads may not touch each other laterally—though axially each bead is forced to contact both of the surfaces to be bonded—hence the term “anisotropic”).
In a high-volume manufacturing environment like the very competitive information storage device industry, there is a practical need for a fast and cost-effective method of bonding many bond pads simultaneously. In particular, there is a need in the art for an improved flexure design that may facilitate the bonding of many bond pads simultaneously or concurrently.